Add CLI with save feature

2 files changed, 95 insertions, 0 deletions

diff --git a/src/cli/cmd/mod.rs b/src/cli/cmd/mod.rs
new file mode 100644
index 0000000..29063e8
--- /dev/null
+++ b/src/cli/cmd/mod.rs
@@ -0,0 +1,53 @@
+//! The commands that can be performed in the CLI
+
+pub mod save;
+
+pub use save::*;
+
+use crate::Editor;
+use std::ops::RangeInclusive;
+
+/// Errors that can occur when parsing a command. This is for syntax checking, the
+/// semantics are checked when trying to execute the command.
+#[allow(missing_docs)]
+#[derive(thiserror::Error, Debug)]
+pub enum CmdParseError {
+    #[error("no command specified")]
+    StringEmpty,
+    #[error("the command {0} is unknown")]
+    NoSuchCmd(String),
+    #[error("wrong number of arguments. Expected in range {1:?}, but received {0}")]
+    WrongNumberOfArgs(usize, RangeInclusive<usize>),
+    #[error("{0} cannot be converted into a {1}, which is required")]
+    InvalidArgType(String, &'static str),
+}
+
+/// Attempts to parse a command from the given string. If it is unsuccessful, it returns a
+/// [CmdParseError].
+pub fn parse_command(string: &str) -> Result<Box<dyn Command>, CmdParseError> {
+    if string.is_empty() {
+        return Err(CmdParseError::StringEmpty);
+    }
+
+    let parts: Vec<&str> = string.split_whitespace().collect();
+    match parts[0] {
+        "w" => Ok(Box::new(Save::from_args(&parts[1..])?)),
+        other => Err(CmdParseError::NoSuchCmd(other.to_owned())),
+    }
+}
+
+/// Indicates that this entity (command) can be created from arguments. Make sure to check what is
+/// expected, to pass the arguments to the correct command.
+pub trait FromArgs: Sized {
+    /// Creates a new instance from the arguments provided. If for whatever reason the syntax of the
+    /// given arguments is correct an [ArgParseError] is returned.
+    fn from_args(args: &[&str]) -> Result<Self, CmdParseError>;
+}
+
+/// A common trait for all commands.
+pub trait Command {
+    /// Process this command on the provided context. Returns either a string with the output of the
+    /// command when everything went right with it, or an error string explaining what went wrong,
+    /// which can be displayed to the user.
+    fn process(&self, editor: &mut Editor) -> Result<String, String>;
+}
diff --git a/src/cli/cmd/save.rs b/src/cli/cmd/save.rs
new file mode 100644
index 0000000..2c022cf
--- /dev/null
+++ b/src/cli/cmd/save.rs
@@ -0,0 +1,42 @@
+//! Save the contents of the map to disk
+
+use super::Command;
+use super::{CmdParseError, FromArgs};
+use crate::map::MapData;
+use crate::Editor;
+use std::path::PathBuf;
+
+/// The save command can take any destination in the filesystem the user can write to. Processing
+/// will then save the map contents to that destination, overwriting anything that may be there.
+pub struct Save {
+    destination: PathBuf,
+}
+
+impl FromArgs for Save {
+    fn from_args(args: &[&str]) -> Result<Self, CmdParseError> {
+        if args.len() != 1 {
+            return Err(CmdParseError::WrongNumberOfArgs(args.len(), 1..=1));
+        }
+
+        Ok(Self {
+            destination: PathBuf::from(args[0]),
+        })
+    }
+}
+
+impl Command for Save {
+    fn process(&self, editor: &mut Editor) -> Result<String, String> {
+        let data = MapData::extract_data(editor.map());
+
+        match data.write_to_file(&self.destination) {
+            Ok(_) => Ok(format!(
+                "Successfully wrote contents to `{:?}`",
+                &self.destination
+            )),
+            Err(e) => Err(format!(
+                "Unable to write to `{:?}`. Error: {:?}",
+                &self.destination, e
+            )),
+        }
+    }
+}